(1) Field of the Invention
The present invention relates to a system and method of use for a broadband transistor switch in periodic switching applications.
(2) Description of the Prior Art
Sensor systems located along fixed or towed tethers need to transmit sensor data to certain types of airborne platforms and certain types of floating sensor systems. Direct Current (DC) power for operation is difficult to supply because of the long length and/or the small size of the sensor tethers. Alternatively, networked sensor systems may comprise thousands of individual sensors, each of which requires power for command, control and communications. Thus, system power at the sensor is at a premium and efficient, reliable, transmitter design is critical to the long term operation of tethered and untethered sensor systems.
In Planer et al. (U.S. Pat. No. 4,443,719), a voltage isolated gate drive circuit for insulated gate semiconductors utilizes a small, inexpensive pulse transformer to provide a rectangular drive wave form. The small pulse transformer can be operated with an input square wave form at relatively low frequencies, such as 60 hertz, and can be operated from a common power supply with the high voltage supplied to the output field effect transistor.
In de Sartre (U.S. Pat. No. 4,645,945), a switching control circuit is provided for power transistors controlling an inductive load. To avoid oversaturation of the transistor, causing excessive consumption and a switching difficulty on opening, said transistor is caused to operate at the limit of saturation, by means of an emitter resistor, a quasi current mirror in parallel across said resistor, another current mirror and a current amplifier. The current from said first current mirror is controlled on or off by a square wave generator such as those used in chopped power supplies or television scanning circuits for which the invention is particularly appropriate.
In Cripe (U.S. Pat. No. 5,276,357), a drive circuit generates a quasi-square wave for use in switching power amplifiers by supplying square wave signals which are 180 degrees out of phase, but otherwise identical, to the respective control inputs of two switching transistors. Opposite ends of the respective controlled paths of the transistors are connected to the input of the device which is being driven. The driven device input has a capacitance associated therewith, which normally results in a voltage loss as this capacitance is alternately charged and discharged. The circuit component values are selected so that this capacitance is charged while the switching transistors have yet to reach their threshold voltages, and thus at the moment when either transistor is switched to a conducting state the voltage across that transistor's controlled path will be substantially zero, and the normal switching loss, which is a product of the square of that voltage, the input capacitance of the driven device, and the operating frequency, is eliminated.
In Miettinen (U.S. Pat. No. 5,530,385), the invention relates to a control circuit for a semiconductor switch, comprising a transformer coupling (T1, T2) for generating AC voltage signals including both control energy and control information, a rectification coupling (DB1, DB2) for rectifying the AC voltage signals generated by the transformer coupling (T1, T2) for generating DC voltage levels (U1, U2, U3) appropriate for turning on and turning off a semiconductor switch (SW1), a first resistor (R2) connected at its first end to a driving electrode of the semiconductor switch (SW1), a second resistor (R1) connected between the driving electrode and the emitter of source electrode of the semiconductor switch, and a booster semiconductor switch (V1) provided between the driving electrode of the semiconductor switch (SW1) and a DC voltage output (U3) generated by the rectification coupling and intended for turning off the semiconductor switch, the driving electrode of the booster semiconductor (V1) being connected to a DC voltage output (U3) generated by the rectification coupling and intended for controlling the booster semiconductor. The control circuit further comprises a zener diode (V2) connected between a second end of the first resistor (R2) and a DC output (U1) generated by the rectification coupling and intended for turning on the semiconductor switch (SW1) and a diode (V4) connected in a forward direction between the turn-off voltage output (U3) of the rectification coupling and the emitter or source electrode of the semiconductor switch (SW1).
In Smith (U.S. Pat. No. 5,686,854), a driver circuit for high frequency transistor type switches, comprising two sections; a positive (+) drive and a negative (−) drive, both sections being supplied with a high frequency signal by a square wave oscillator source. The sections are connected in parallel to a control generated input drive signal. In the negative drive section, the input drive signal is first inverted before being processed. Each section contains precise circuits for routing a high frequency carrier signal, for increasing input drive signal power gain, for providing independent positive and negative slope control, for providing exceptionally high voltage and noise isolation to avoid transmission of harmful voltages or noise, and for delivering a positive or negative drive signal to the gate/emitter of an external transistor under drive. The invention is characterized by its high voltage and noise isolation, using a few components and being small in size.